In the past, LCDs have been used in a wide variety of environments, including displays within the cockpit of an aircraft. In some aircraft, it is desirable to have touch screen LCDs. Many of these touch screen displays use transparent and conductive layers across the viewing surface to effect the touch screen capabilities. Other prior art systems use pairs of light transmitters and detectors disposed around the periphery of the display. These light transmitter and detector pairs are similar to what is shown in U.S. Pat. No. 3,775,560 assigned to the University of Illinois Research Foundation.
While these LCD touch screen systems may have many advantages in particular uses, they also have created challenges. One common challenge created by the conductive layer type touch screen sensor is the degradation of the image to be viewed. Another problem with the prior art light transmitter/sensor pair type of touch screen, in addition to the relatively high cost, occurs when these light transmitter/sensor pairs are used when a pilot is using a night vision imaging system, hereafter NVIS. These light transmitters can interfere with the optimal performance of an NVIS.
Consequently, there exists a need for improved methods and apparatus for data entry into LCDs, via touch screens.